System and method for determining power consumption

ABSTRACT

A system and method is provided to measure the power consumption of circuits whereby, in one aspect, a processor&#39;s temperature is maintained so that its power consumption is measured at the point the processor throttles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/330,887, filed on Dec. 9, 2008, now U.S. Pat. No. 8,037,325, thedisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Processors are comprised of individual circuits such as transistors, andeach operation performed at a circuit typically requires at least asmall amount of power. The operation of a circuit often generates asmall amount of heat as a byproduct. While each individual circuit mayuse relatively little power and generate relatively little heat, currentprocessors include millions—and often hundreds of millions—of denselypacked circuits. The amount of heat generated by the processor furtherincreases as the demands on the processor increase because more circuitsare used more often. If the processor becomes too hot, the heat maydamage the circuits.

A number of different systems and methods have been used to mitigatethis problem. For example, some chips decrease the usage of theircomponents (known as “throttling”) to prevent overheating. For example,a chip may decrease its clock speed so that the operations are performedmore slowly, which gives the chip a little more time to cool down. Thechip may also decrease the number of components it uses to performoperations. The chip may use other techniques as well, either alone orin combination with the foregoing techniques.

Typically, chips throttle when they reach a certain temperature, or atleast assume that they reached or are approaching a particulartemperature by monitoring their circuit usage. It is often preferable toprevent a chip from reaching the throttling stage because it indicatesthat the chip is working at less than peak efficiency.

Reducing the temperature of the chip's environment can help preventoverheating and throttling. For example, a computer may be placed in anair-conditioned location and a fan used to blow the cooler air acrossthe processors in the computer. Other cooling methods are alsoavailable, such as liquid cooling.

Because not all processors are the same, it is helpful to know how muchheat the processor will generate when designing a cooling system for theprocessor. Cooling systems can be expensive, which means that making asystem cooler than necessary can result in unwarranted expense (e.g.,faster fans often cost more than slower ones). On the other hand, if thesystem is not cool enough, the processor may get too hot and throttle.

Accordingly, to help system designers, processor manufactures will oftendefine the “Total Dissipated Power” (TDP) of a processor. However, thisinformation tends to define a distribution curve with a high variationacross individual processors, which can prevent system designers fromdesigning for the reasonable worst case. For example, if the TDPindicates an average power consumption of 80 watts and the coolingsystem is perfectly designed for the average, then many of theprocessors will underperform.

Some systems and methods measure the power consumed by processors whenrunning programs. However, such systems unsatisfactorily address issuesassociated with the thermal aspects of the processor and, thus, can beunpredictable. For example, some systems and methods measure theconsumed power in a way that changes depending on the temperature of thesurrounding environment, thus requiring replication of the externalenvironment in order to provide results that can be meaningfullycompared with other processors.

BRIEF SUMMARY OF THE INVENTION

One aspect of method in accordance with the invention determines thepower consumption of a processor having a clock speed. The methodincludes supplying power to a processor, whereby the amount of powerapplied to the processor changes over time. It also includes regulatingthe amount of external cooling applied to the processor so as to causethe processor to periodically decrease and increase its clock speed. Yetfurther, it determines the amount of power to the processor when thelength of time associated with the decreased clock speed and length oftime associated with the increased clock speed reach a predeterminedcharacteristic.

In another aspect of the invention, a system is provided that includes:a circuit; a device such as but not limited to a fan for cooling thecircuit; a power source such as but not limited to a voltage regulatorfor providing power to the circuit; a controller such as but not limitedto a microprocessor in communication with the cooling device so as tocontrol the performance of the circuit by regulating the cooling device;and a user output such as but not limited to a display to provide, to auser, information related to the power supplied by the power source tothe circuit when the performance of the circuit reaches a predeterminedthreshold.

In yet another aspect of the invention, a method is provided todetermine the power consumption of a circuit, wherein the temperature ofthe circuit depends on the amount of operations performed by the circuitand wherein the circuit decreases the amount of the operations itperforms depending on the temperature. The method includes: supplyingpower to the circuit; changing the ambient temperature of the circuituntil a predetermined threshold is achieved, wherein the threshold isbased on (1) the amount of time the circuit is not decreasing the amountof operations due to the temperature of the circuit relative to (2) theamount of time the circuit is decreasing the amount of operations due tothe temperature of the circuit; and determining the power consumptionwhen the threshold is achieved.

Other aspects of the invention are described below.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a system diagram of an aspect of the invention.

FIG. 2 is a flow chart of an aspect of the invention.

FIG. 3 is a flow chart of an aspect of the invention.

DETAILED DESCRIPTION

One aspect of the invention provides a system and method for determiningthe power consumed by a processor so that an appropriate cooling systemcan be designed. The processor is stressed, and allowed to heat andcool, until it reaches a desired state of throttling versusnon-throttling, at which point its power consumption is measured.

A system 100 in accordance with an aspect of the invention is shown inFIG. 1. The system includes a test processor 110 with access to programsin memory 115 (such as a hard drive), voltage regulator 120, controller130 and cooling device 140.

Test processor 110 is a processor whose performance with respect tothermal characteristics is to be tested. It will be understood thatprocessor 110 is not limited to any particular type of processor, andmay thus be a general purpose microprocessor, ASIC, integrated circuit,or a circuit whose performance is controllable to reduce its thermaloutput. In one aspect, the circuit to be tested is a microprocessor fora general purpose computer such as a server or personal computer.

Test processor 110 includes inputs and outputs, such as pins.

In one aspect of the system and method, one of those outputs is a valueindicative of the extent to which the processor has decreased itsoperations due to the temperature (actual or assumed) of all or aportion of the processor. In that regard, the output may comprise athrottle pin 117. For example, certain Intel processors provide a pinthat outputs a signal having one of two values indicating whether thechip is throttling (e.g., the pin outputs a 0V signal) or is notthrottling (e.g., the pin outputs a 3V signal).

System 100 further includes a source of power to the test processor suchas voltage regulator 120. Oftentimes, the processor will draw more poweras it performs more operations. Typically, the additional power isconsumed by drawing more current rather than changing the voltage, butcertain processor may vary voltage demands as well.

Voltage regulator 120 outputs a value that indicative of the powerprovided to the processor 110.

The system shown in FIG. 1 also includes a controller 130. Thecontroller may have access to a memory 132 storing data 134 andinstructions 133. The instructions are executable by a processor 135 orsimilar circuitry. In accordance with those instructions, the processoris capable of retrieving and storing data 134. For example, a generalpurpose microcontroller, such as Atmel's ATmega8 microcontroller, may beprogrammed with instructions performing the functions described below.

The controller accepts different information as input. For example, itmay accept information indicative of the performance of the processor110 based on the temperature, such as by directly or indirectlyreceiving the signal at throttle pin 117. Similarly, it may acceptinformation indicative of the power consumed by the processor, such asby directly or indirectly receiving the signal output by voltageregulator 120 that indicates the power supplied to the processor 110.

The values received by the controller may be stored in data 134.

The controller 130 may also send a signal (not shown) to the processor110 and voltage regulator 120 instructing them to turn on and beginoperating.

System 100 also includes a device for cooling the test processor 120. Asshown in FIG. 1, the device may be a fan 140 passing cooler air 145 overthe processor 110.

Fan 140 operates under the control of controller 130. In one aspect, thefan is controlled by PWM whereby the controller sends a series of pulsesto the fan to turn on or off; the closer the pulses, the faster the fanturns and the more cooling it provides. In another aspect, thecontroller sends a desired RPM, which the fan implements.

System 100 further includes a user output device in direct or indirectcommunication with controller 130 so as to provide, to users,information that is accessible by the controller. As shown by the dashedarrow between the voltage regulator 120 and display 130 in FIG. 1, theoutput may thus indirectly convey information received from voltageregulator 120 or, alternatively, may be connected directly to thevoltage regulator. The output is not limited to any particular device,but may comprise any device capable of conveying information to a usersuch as but not limited to a monitor, printer, speaker, or communicationline that provides information directly or indirectly to the foregoing.

In addition to the operations illustrated in FIGS. 2 and 3, variousoperations in accordance with a variety of aspects of the invention willnow be described. It should be understood that the following operationsdo not have to be performed in the precise order described below.Rather, various steps can be handled in reverse order or simultaneously.

The process may begin by connecting the processor to be tested to theother units of the system as applicable. This may include, but is notlimited to, mounting test processor 110 on a motherboard on which theother components of the system are also mounted. The startingtemperature of the system may be ambient temperature and the motherboardstored in an open chassis.

The test processor 110 loads a test program from memory 115 (such as ahard drive or other memory device) or otherwise accesses a set ofinstructions to be executed by the processor 110 (e.g., instructionsthat are prestored in the chip). In one aspect of the system and method,the test program is a stress test designed to tax the processor'sprocessing abilities to the limit by making as many circuits of the testprocessor as busy as practical.

Voltage regulator 120 provides power to the test processor 110 as itexecutes instructions. The amount of power will tend to increase overtime as the test processor 110 operates more circuits. A certain amountof this power may be lost in the form of heat.

As the amount of power consumed by the test processor changes over atime, voltage regulator 120 outputs this amount to controller 130. Inaccordance with instructions 133, the processor 135 of controller 130monitors the amount of power and logs it as data 134.

Controller 130 also monitors the throttle pin 117 of test processor 110.For example, the signal from the throttle pin may be sampled 1,000 timesa second. In one aspect of the invention, the samples are stored in data134. In another aspect of the invention, the samples are not storeduntil the signal indicates that throttling has begun.

In one aspect of the system and method and during the initial stages,the cooling device of the system and method is set to allow theprocessor being tested to heat up. For example, the fan 140 may beswitched off, or run at a low speed (such as 2000 rpm at an ambienttemperature of 25 C), from the beginning of the test until thecontroller receives the first indication that the processor isthrottling.

At some point, the processor will start to throttle. In the system shownin FIG. 1, this will be indicated by the signal at the throttle pingoing from high to low.

Rather than letting the processor throttle indefinitely, the controller130 will cool the processor. One system and method in which this may beaccomplished is to change the ambient temperature of the processor, suchas by activating the cooling device to apply more coolant to theprocessor. For example, the RPM of the fan 140 may be increased to blowmore cool air across the processor 110. One method of accomplishing thisis for the instructions 133 to tie the PWM fan signal, directly orindirectly, to the signal received from the throttle pin. This maycontinue until the throttling ceases.

When the controller 130 determines that the throttling has ceased, thecontroller may diminish the cooling until the processor begins tothrottle again.

This process (allowing the processor to heat until it throttles, coolingthe processor until it stops throttling, and then allowing the processorto heat up again) may be repeated numerous times.

The controller brings the test processor to a point of controlledthrottling. For example, the controller 130 may control the speed of fan140 until the processor spends as much time throttling as not (i.e., a50% duty cycle). In that regard, the controller may sample the signal atthe throttle pin and adjust the fan speed higher or lower depending onwhether most of samples indicate throttling or not throttling.

Once the controller determines that the processor is at a desired statewith respect to throttling, the controller may store a benchmarkassociated with the processor's power consumption. For example, if the50% duty cycle is achieved for approximately 5 minutes, the controllermay assign and store a benchmark in data 134 equivalent to the powerthen being consumed by the test processor (e.g., 90 watts).

The process may be repeated for multiple processors. In one aspect, whena new model of processors is purchased in bulk, a sample number (e.g.,100) out of a bin (e.g., 10,000) may be tested and their powerconsumption benchmarks stored. Using the foregoing example, the 100processors may have benchmarks in the range of 80 to 94 watts.

The power consumption benchmarks may be used to design the coolingsystem. Whether the system is being defined for an individual processoror the worst-case of a bin of processors, the cooling system may bedesigned accordingly. Once the system is designed in accordance with thecharacteristics of the worst (from a power consumption point of view)processor in the bin, the thermal solution will typically be sufficientfor any processor in the bin.

As will be seen, one system and method in accordance with the inventionallows the creation of a power consumption benchmark that existsindependent of the cooling system. In this aspect, the surroundingtemperature does not affect the benchmark because the processor ismeasured at its throttling point regardless of the external temperature.One manner in which this may be achieved is to use a controller toregulate the performance of the circuit by controlling a cooling device.

One of the advantages of the present invention is its ability toaccommodate a wide variety of alternatives.

For example, rather than relying on the throttle signal as input, thecontroller may rely on other performance indicators such as clock speed.Some aspects may also measure and rely on the external temperature ofthe CPU; however, some of those aspects may not have the feature ofbeing independent of external temperature. Combinations of one or moreof the foregoing may also be used.

Similarly, using a 50% throttling duty cycle is particularlyadvantageous because the processor is measured at a point where it isedge of the throttling; it is throttling and not throttling in equalmeasure. However, percentages above and below 50% may be used as welland provide their own advantages depending on system design preferences.Moreover, the target with respect to throttling need not be a directratio based on the time spent throttling versus non-throttling time.

Alternatives of the system shown in FIG. 1 are also possible. By way ofexample only, rather than using a single controller 130, a separate anddedicated fan controller may be tied to the throttle pin, and a displaymay be connected to the power supply.

Yet further, in certain aspects of the system and method, thetemperature of the circuit may also be heated as well as (or instead of)cooled in order to bring (or more quickly bring) the circuit to atemperature wherein it throttles.

Most of the foregoing alternative embodiments are not mutuallyexclusive, but may be implemented in various combinations to achieveunique advantages. As these and other variations and combinations of thefeatures discussed above can be utilized without departing from theinvention as defined by the claims, the foregoing description of theembodiments should be taken by way of illustration rather than by way oflimitation of the invention as defined by the claims.

1. A method of determining the power consumption of a processor having aclock speed comprising: supplying power to a processor, whereby theamount of power applied to the processor changes over time; regulatingthe amount of external cooling applied to the processor so as to causethe processor to periodically decrease and increase its clock speed;determining the amount of power to the processor when the length of timeassociated with the decreased clock speed and length of time associatedwith the increased clock speed reach a predetermined characteristic. 2.The method of claim 1 wherein the characteristic comprises the length oftime associated with the decreased clock speed being relatively equal tothe length of time associated with the increased clock speed.
 3. Themethod of claim 1 wherein the external cooling is regulated by a fan. 4.The method of claim 1 wherein the fan speed is increased and decreasedbased on said lengths of time.